[hooks] Add baseUri to user defines

pkgs/hooks/CHANGELOG.md

@@ -3,6 +3,8 @@
 - Add `ProtocolExtension.setupLogger`, which the hooks runner calls to provide
   the logger used for validation diagnostics before any other method is invoked
   on the extension.
+- Add `HookInputUserDefines.baseUri`, which can be used to resolve paths
+  from nested user-defined options.
 
 ## 2.1.0
 

pkgs/hooks/lib/src/config.dart

@@ -225,17 +225,21 @@ final class HookInputUserDefines {
   /// Then:
   /// - `input.userDefines['enable_experimental_features']` returns `true`.
   /// - `input.userDefines['optimization_level']` returns `"O3"`.
-  Object? operator [](String key) {
-    final syntaxNode = _input._syntax.userDefines;
-    if (syntaxNode == null) {
-      return null;
-    }
-    final packageUserDefines = PackageUserDefinesSyntaxExtension.fromSyntax(
-      syntaxNode,
-    );
-    final pubspecSource = packageUserDefines.workspacePubspec;
-    return pubspecSource?.defines[key];
-  }
+  Object? operator [](String key) => _findDefine([key])?.$1;
+
+  /// An absolute [Uri] that can be used to interpret user-defines as paths.
+  ///
+  /// This uses the [keyPathDefine] to traverse available options, starting at
+  /// the root. If the key path contains a string, this enters a YAML map. For
+  /// an integer element, this enters a YAML sequence. Any other key path
+  /// element is invalid and throws.
+  /// If no element exists for any position in the key path, null is returned.
+  ///
+  /// This is a generalized variant of [path] returning the base URI for all
+  /// options under [keyPathDefine]. To resolve a top-level string option as a
+  /// path, use [path] directly.
+  Uri? baseUri(List<Object /* String|int */> keyPathDefine) =>
+      _findDefine(keyPathDefine)?.$2.basePath;
 
   /// Resolves the relative path provided in the user-define for [key] to an
   /// absolute [Uri] pointing to the file or directory on the host filesystem.
@@ -268,11 +272,30 @@ final class HookInputUserDefines {
   ///   // Read assets from the directory...
   /// }
   /// ```
+  ///
+  /// See also:
+  ///
+  ///  - [baseUri], which returns the equivalent of [Uri.base] for the source
+  ///    defining a key (e.g. the directory containing a workspace pubspec with
+  ///    a `hooks` entry). Unlike this method, which directly interprets a
+  ///    value as a path, the base uri can be used to [Uri.resolve] arbitrary
+  ///    path values.
   Uri? path(String key) {
+    if (_findDefine([key]) case (final String value, final source)?) {
+      return source.basePath.resolve(value);
+    }
+
+    return null;
+  }
+
+  (Object, PackageUserDefinesSource)? _findDefine(
+    Iterable<Object?> keyPathDefine,
+  ) {
     final syntaxNode = _input._syntax.userDefines;
     if (syntaxNode == null) {
       return null;
     }
+
     final packageUserDefines = PackageUserDefinesSyntaxExtension.fromSyntax(
       syntaxNode,
     );
@@ -284,9 +307,32 @@ final class HookInputUserDefines {
     // TODO(https://github.com/dart-lang/native/issues/2215): Add commandline
     // arguments.
     for (final source in sources) {
-      final relativepath = source.defines[key];
-      if (relativepath is String) {
-        return source.basePath.resolve(relativepath);
+      Object? options = source.defines;
+
+      for (final (i, key) in keyPathDefine.indexed) {
+        if (key is String) {
+          if (options is Map) {
+            options = options[key];
+          } else {
+            return null;
+          }
+        } else if (key is int) {
+          if (options is List) {
+            options = options[key];
+          } else {
+            return null;
+          }
+        } else {
+          throw ArgumentError.value(
+            keyPathDefine,
+            'keyPathDefine',
+            'Must contain only strings or ints (found `$key` at index $i).',
+          );
+        }
+      }
+
+      if (options != null) {
+        return (options, source);
       }
     }
     return null;

pkgs/hooks_runner/test/test_data/user_defines_test.dart

@@ -39,6 +39,14 @@ void main() async {
       // The native assets build runner must be reinvoked if the pubspec
       // changes, as the pubspec could contain user-defines.
       expect(result.dependencies, contains(pubspecUri));
+      expect(
+        result.dependencies,
+        contains(packageUri.resolve('assets/data.json')),
+      );
+      expect(
+        result.dependencies,
+        contains(packageUri.resolve('assets/second.json')),
+      );
     }),
   );
 }

pkgs/hooks_runner/test_data/manifest.yaml

@@ -260,6 +260,7 @@
 - use_all_api/hook/link.dart
 - use_all_api/pubspec.yaml
 - user_defines/assets/data.json
+- user_defines/assets/second.json
 - user_defines/bin/user_defines.dart
 - user_defines/hook/build.dart
 - user_defines/pubspec.yaml

pkgs/hooks_runner/test_data/user_defines/assets/second.json

@@ -0,0 +1,3 @@
+{
+    "foo": "bar"
+}

pkgs/hooks_runner/test_data/user_defines/hook/build.dart

@@ -31,5 +31,24 @@ void main(List<String> arguments) async {
     }
     final file = File.fromUri(someFile);
     output.dependencies.add(file.uri);
+
+    final base = input.userDefines.baseUri([
+      'nested',
+      'options',
+      'paths',
+      0,
+    ]);
+    if (base == null) {
+      throw Exception(
+        'User-define nested.options.paths.0 does not have the right value: '
+        '${input.userDefines['nested']}.',
+      );
+    }
+
+    final pathOption =
+        (((input.userDefines['nested'] as Map)['options'] as Map)['paths']
+                as List)[0]
+            as String;
+    output.dependencies.add(base.resolve(pathOption));
   });
 }

pkgs/hooks_runner/test_data/user_defines/pubspec.yaml

@@ -27,5 +27,9 @@ hooks:
       user_define_key2:
         foo: bar
       some_file: assets/data.json
+      nested:
+        options:
+          paths:
+            - assets/second.json
     some_other_package: # package name
       user_define_key3: user_define_value3